Hitherto, it has been known that an obstruction detecting device is fastened to a cutter head in the leading portion of a civil engineering machine such as a shield machine so as to transmit electromagnetic waves and to receive waves reflected from a buried article for the purpose of detecting it. Therefore, a transmission antenna and a receiving antenna are fastened to the rotary cutter head so as to transmit a detected signal to a non-rotary shield body disposed in the rear portion via a slip ring, the detected signal being then calculated by an attached computer. The results of the calculations are displayed so that the presence of the buried article is detected.
However, the fact that the impedance matching of high frequency cannot be established with the aforesaid conventional electric connection method which uses the slip ring disables a high frequency signal of hundreds MHz to be transmitted. Therefore, a conversion to a low frequency is made before the transmission is performed. However, the efficiency is unsatisfactory and the cost cannot be reduced. What is worse, the electric connection established by using the slip ring can easily be affected by noise generated at the contact or by external noise, causing a problem to arise in that it is difficult to transmit analogue signals or signals of relatively high frequencies with reliability.
As a means for making waveform information of an underground radar visible, there are a first method (A-scope image) wherein an oscilloscope is so arranged that the waveform is drawn while making the axis of abscissa stand for time (the depth) and the axis of ordinate stand for the intensity, and another method (B-scope image) so arranged that the intensity of the signal is modulated while making the axis of ordinate stand for time (the depth) and the axis of abscissa stand for the distance so that a dark and light two dimensional image is drawn. However, there is a problem in that an unskilled operator cannot detect the accurate position of the buried article because dark and light fringe patterns are drawn on the display device due to the fact that reflected signals from multiple underground portions superpose on one another.
Furthermore, the conventional civil engineering machine such as the shield machine necessitates a backfilling work to be performed in such a manner that a void generated due to the excavation is filled with quick hardening concrete or the like for the purpose of preventing settlement of the ground level. In order to prevent the rupture of the natural ground around the tail, the back-filling work is performed in such a manner that filling is performed simultaneously with or immediately after the shield driving has been performed while completely filling the tail void. In the aforesaid backfilling work, the filling pressure and the filling amount are factors to be controlled.
However, the fact that the back-filling work in the conventional shield method has been so arranged that the size of the void is not included in the factors to be controlled causes a risk that back-filling work cannot be correctly performed. For example, filling by an amount smaller than a specified amount can be performed due to stop of the front portion in a case where the filling supply source pressure is controlled. In a case where the filling amount is controlled, there is a fear that the road surface is torn off, or that excavation becomes difficult because the filling material reaches the working face, or that the road surface caves in if the filling material has not been filled into a proper position. What is worse, a discrimination cannot be made as to whether or not the filling material has reached the working face even if the filling material is in a quantity larger than a specified quantity because the back-filling amount is changed depending upon the drive force, the specific gravity of the soil, the cutting force of the cutter and the type of the soil which is being excavated. There arises another problem in that the excavation becomes difficult if the filling pressure is excessively high because the filling material reaches the working face.
Accordingly, an object of the present invention is to provide a system and a method for transmitting and calculating data in a shield machine capable of transmitting analog signals or signals having relatively high frequencies with reliability while eliminating an influence of noise, enabling an unskilled operator to know the accurate position of a buried article, and accurately perform void filling work.